Intrathecal Baclofen Toxicity Mimicking Nonconvulsive Status Epilepticus (P6.026)

Introduction Intrathecal baclofen pumps have been available for use in the U.S. since 1992 for spinal cord origin spasticity and over sixty thousand are now used worldwide. Pump malfunctions generally lead to drug withdrawal, though few cases have described toxicity. Case Report A 54 year-old male, with a history of central cord syndrome with spastic paraparesis, presented after being found unresponsive. He had an intrathecal baclofen pump, with normal regular interrogations. His last refill was the day prior to presentation. He was in his usual state of health earlier that day. Following intubation in the emergency department for airway protection, exam revealed intact brainstem reflexes, blink to threat, upper extremity withdrawal to pain, normal tone and brisk reflexes. On admission, an electroencephalogram was ordered out of concern for NCSE. This showed burst suppression with frequent epileptiform discharges. Maximum anti-epileptic treatment was given, which did not improve the EEG pattern. The pump was turned off out of concern for overdose. Unfortunately, the patient continued to decline and expired five days later in multi-organ failure. Post-mortem, pump medication was extracted and was 18mL (9.95mg, 25 times daily dose) short of expected amount. Discussion Baclofen has presynaptic GABA-B receptor agonist effects, lending it excitatory and inhibitory properties. Therefore, seizures can result from both toxicity and withdrawal. Common signs and symptoms of toxicity include somnolence, hypotonia, bradycardia, hyporeflexia and mydriasis. Additionally, toxicity has known electroencephalographic effects, including burst suppression with generalized epileptiform discharges, background slowing and quasiperiodic generalized epileptiform activity. In our case, treatment for NCSE was initiated, as there was no proof of drug toxicity and untreated status epilepticus is life-threatening. EEG evidence, plus the large amount of drug missing from the pump post-mortem, retrospectively supported the diagnosis of large dose intrathecal baclofen toxicity. There is no proven specific antidote for baclofen overdose. Disclosure: Dr. Zieman has nothing to disclose. Dr. Burns has nothing to disclose.